ref: 43bf50d093b48ad481fc24656b66d34422ac07dc
dir: /jbig2_huffman.c/
/*
jbig2dec
Copyright (c) 2001 artofcode LLC.
This program is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 2 of the License, or
(at your option) any later version.
$Id: jbig2_huffman.c,v 1.7 2001/07/05 22:37:44 giles Exp $
*/
/* Huffman table decoding procedures
-- See Annex B of the JBIG2 draft spec */
#include <stdlib.h>
#include "jbig2dec.h"
#include "jbig2_huffman.h"
#define JBIG2_HUFFMAN_FLAGS_ISOOB 1
#define JBIG2_HUFFMAN_FLAGS_ISLOW 2
#define JBIG2_HUFFMAN_FLAGS_ISEXT 4
struct _Jbig2HuffmanState {
/* The current bit offset is equal to (offset * 8) + offset_bits.
The MSB of this_word is the current bit offset. The MSB of next_word
is (offset + 4) * 8. */
uint32 this_word;
uint32 next_word;
int offset_bits;
int offset;
Jbig2WordStream *ws;
};
Jbig2HuffmanState *
jbig2_huffman_new (Jbig2WordStream *ws)
{
Jbig2HuffmanState *result = (Jbig2HuffmanState *)malloc (sizeof(Jbig2HuffmanState));
result->offset = 0;
result->offset_bits = 0;
result->this_word = ws->get_next_word (ws, 0);
result->next_word = ws->get_next_word (ws, 4);
result->ws = ws;
return result;
}
int32
jbig2_huffman_get (Jbig2HuffmanState *hs,
const Jbig2HuffmanTable *table, bool *oob)
{
Jbig2HuffmanEntry *entry;
byte flags;
int offset_bits = hs->offset_bits;
uint32 this_word = hs->this_word;
uint32 next_word;
int RANGELEN;
int32 result;
for (;;)
{
int log_table_size = table->log_table_size;
int PREFLEN;
entry = &table->entries[this_word >> (32 - log_table_size)];
flags = entry->flags;
PREFLEN = entry->PREFLEN;
next_word = hs->next_word;
offset_bits += PREFLEN;
if (offset_bits >= 32)
{
Jbig2WordStream *ws = hs->ws;
this_word = next_word;
hs->offset += 4;
next_word = ws->get_next_word (ws, hs->offset + 4);
offset_bits -= 32;
hs->next_word = next_word;
PREFLEN = offset_bits;
}
this_word = (this_word << PREFLEN) |
(next_word >> (32 - offset_bits));
if (flags & JBIG2_HUFFMAN_FLAGS_ISEXT)
{
table = entry->u.ext_table;
}
else
break;
}
result = entry->u.RANGELOW;
RANGELEN = entry->RANGELEN;
if (RANGELEN > 0)
{
int32 HTOFFSET;
HTOFFSET = this_word >> (32 - RANGELEN);
if (flags & JBIG2_HUFFMAN_FLAGS_ISLOW)
result -= HTOFFSET;
else
result += HTOFFSET;
offset_bits += RANGELEN;
if (offset_bits >= 32)
{
Jbig2WordStream *ws = hs->ws;
this_word = next_word;
hs->offset += 4;
next_word = ws->get_next_word (ws, hs->offset + 4);
offset_bits -= 32;
hs->next_word = next_word;
RANGELEN = offset_bits;
}
this_word = (this_word << RANGELEN) |
(next_word >> (32 - offset_bits));
}
hs->this_word = this_word;
hs->offset_bits = offset_bits;
if (oob != NULL)
*oob = (flags & JBIG2_HUFFMAN_FLAGS_ISOOB);
return result;
}
#define LOG_TABLE_SIZE_MAX 8
Jbig2HuffmanTable *
jbig2_build_huffman_table (const Jbig2HuffmanParams *params)
{
int LENCOUNT[256];
int LENMAX = -1;
const Jbig2HuffmanLine *lines = params->lines;
int n_lines = params->n_lines;
int i, j;
int log_table_size = 0;
Jbig2HuffmanTable *result;
Jbig2HuffmanEntry *entries;
int CURLEN;
int firstcode = 0;
int CURCODE;
int CURTEMP;
/* B.3, 1. */
for (i = 0; i < params->n_lines; i++)
{
int PREFLEN = lines[i].PREFLEN;
int lts;
if (PREFLEN > LENMAX)
{
for (j = LENMAX + 1; j < PREFLEN + 1; j++)
LENCOUNT[j] = 0;
LENMAX = PREFLEN;
}
LENCOUNT[PREFLEN]++;
lts = PREFLEN + lines[i].RANGELEN;
if (lts > LOG_TABLE_SIZE_MAX)
lts = PREFLEN;
if (lts <= LOG_TABLE_SIZE_MAX && log_table_size < lts)
log_table_size = lts;
}
result = (Jbig2HuffmanTable *)malloc (sizeof(Jbig2HuffmanTable));
result->log_table_size = log_table_size;
entries = (Jbig2HuffmanEntry *)malloc (sizeof(Jbig2HuffmanEntry) << log_table_size);
result->entries = entries;
LENCOUNT[0] = 0;
for (CURLEN = 1; CURLEN <= LENMAX; CURLEN++)
{
int shift = log_table_size - CURLEN;
/* B.3 3.(a) */
firstcode = (firstcode + LENCOUNT[CURLEN - 1]) << 1;
CURCODE = firstcode;
/* B.3 3.(b) */
for (CURTEMP = 0; CURTEMP < n_lines; CURTEMP++)
{
int PREFLEN = lines[CURTEMP].PREFLEN;
if (PREFLEN == CURLEN)
{
int RANGELEN = lines[CURTEMP].RANGELEN;
int start_j = CURCODE << shift;
int end_j = (CURCODE + 1) << shift;
byte eflags = 0;
/* todo: build extension tables */
if (params->HTOOB && CURTEMP == n_lines - 1)
eflags |= JBIG2_HUFFMAN_FLAGS_ISOOB;
if (CURTEMP == n_lines - (params->HTOOB ? 3 : 2))
eflags |= JBIG2_HUFFMAN_FLAGS_ISLOW;
if (PREFLEN + RANGELEN > LOG_TABLE_SIZE_MAX)
{
for (j = start_j; j < end_j; j++)
{
entries[j].u.RANGELOW = lines[CURTEMP].RANGELOW;
entries[j].PREFLEN = PREFLEN;
entries[j].RANGELEN = RANGELEN;
entries[j].flags = eflags;
}
}
else
{
for (j = start_j; j < end_j; j++)
{
int32 HTOFFSET = (j >> (shift - RANGELEN)) &
((1 << RANGELEN) - 1);
if (eflags & JBIG2_HUFFMAN_FLAGS_ISLOW)
entries[j].u.RANGELOW = lines[CURTEMP].RANGELOW -
HTOFFSET;
else
entries[j].u.RANGELOW = lines[CURTEMP].RANGELOW +
HTOFFSET;
entries[j].PREFLEN = PREFLEN + RANGELEN;
entries[j].RANGELEN = 0;
entries[j].flags = eflags;
}
}
CURCODE++;
}
}
}
return result;
}
#ifdef TEST
#include <stdio.h>
/* a test bitstream, and a list of the table indicies
to use in decoding it. 1 = table B.1 (A), 2 = table B.2 (B), and so on */
/* this test stream should decode to { 8, 5, oob, 8 } */
const byte test_stream[] = { 0xe9, 0xcb, 0xf4, 0x00 };
const byte test_tabindex[] = { 4, 2, 2, 1 };
static uint32
test_get_word (Jbig2WordStream *self, int offset)
{
/* assume test_stream[] is at least 4 bytes */
if (offset+3 > sizeof(test_stream))
return 0;
else
return ( (test_stream[offset] << 24) |
(test_stream[offset+1] << 16) |
(test_stream[offset+2] << 8) |
(test_stream[offset+3]) );
}
int
main (int argc, char **argv)
{
Jbig2HuffmanTable *tables[5];
Jbig2HuffmanState *hs;
Jbig2WordStream ws;
bool oob;
int32 code;
tables[0] = NULL;
tables[1] = jbig2_build_huffman_table (&jbig_huffman_params_A);
tables[2] = jbig2_build_huffman_table (&jbig_huffman_params_B);
tables[3] = NULL;
tables[4] = jbig2_build_huffman_table (&jbig_huffman_params_D);
ws.get_next_word = test_get_word;
hs = jbig2_huffman_new (&ws);
printf("testing jbig2 huffmann decoding...");
printf("\t(should be 8 5 (oob) 8)\n");
{
int i;
int sequence_length = sizeof(test_tabindex);
for (i = 0; i < sequence_length; i++) {
code = jbig2_huffman_get (hs, tables[test_tabindex[i]], &oob);
if (oob) printf("(oob) ");
else printf("%d ", code);
}
}
printf("\n");
return 0;
}
#endif